(a) Field of the Invention
The present invention relates to a densitometer to be used for processing fractionated patterns of sera formed with electrophoretic apparatus.
(b) Description of the Prior Art
FIG. 1 shows a basic pattern of concentration distribution i.e., densitogram of a fractionated pattern formed by electrically energizing a carrier made of cellulose acetate film onto which man's serum is applied (a healthy man's serum generally shows this pattern). Such an electrophoretic pattern usually consists of five fractions of A, B, C, D and E including five peaks of a.sub.0, A.sub.1, a.sub.2, a.sub.3 and a.sub.4 which correspond to albumin (A), alpha 1 globulin (B), alpha 2 globulin (C), beta globulin (D) and gamma globulin (E) respectively. Diagnosis or distinguishment between normality and abnormality is done on the basis of an analog pattern and percentages of integrals of the individual fractions relative to that of the entire pattern. However, patterns of concentration distribution on fractionated patterns of actual samples may include peaks produced by various causes in addition to those illustrated in FIG. 1. The pattern shown in FIG. 2, for example, has a peak designated as a.sub.5 in addition to the abovementioned five peaks and consists of six fractions showing a boundary point b.sub.5 in addition to the regular boundary points of b.sub.1, b.sub.2, b.sub.3 and b.sub.4. The boundary point b.sub.5 is formed depending on freshness of the serum due to a certain component of the serum, namely beta.sub.1c globulin which is fractionated by the electrophoresis. Further, the pattern shown in FIG. 3 has no boundary point corresponding to b.sub.4, and consists of only four fractions having boundary points of b.sub.1, b.sub.2 and b.sub.3.
In case where a sample produces a pattern consisting of six or more fractions including peak(s) in addition to the five basic ones shown in FIG. 1 or consisting of four fractions, inconvenience is caused in automatic processing of colorimetric data with a computer. FIG. 4 shows an example of a configuration of a densitometer and a photometric apparatus which are currently used. In the block diagram shown in FIG. 4, the light emitted from a light source 3 is passed through a lens 4, a filter 5 and a slit 6, used for irradiating a carrier 1 and detected with a photo detector element 7. The carrier 1 has fractionated patterns of sera 2, 2', 2". . . formed thereon as shown in FIG. 5, and is placed between the light source and the photo detector for photometry of the individual fractionated patterns while scanning in the direction perpendicular to the shifting direction of the carrier. That is to say, the light emitted from the light source and passing through the sample (fractionated pattern of a serum) is received by the photo detector element 7, whose output corresponding to sample concentration is amplified with a preamplifier 8, converted by a logarithmic converter 9 into logarithmic values for preparing an analog densitogram as shown in FIG. 1 and so on. Successively, outputs from the logarithmic converter 9 are inputted into an A/D converter 10 and converted into digital signals at definite time intervals by operating a conversion command signal generator 11 with photometry commands 11a from a computer 12. On the basis of the digital data obtained at this stage, percentage of integral of each fraction relative to that of the entire pattern is determined.
In the operations described above, it is possible to determine the boundary points by calculating minimum values in case of a densitogram traced based on an electrophoretic pattern consisting of five fractions as examplified in FIG. 1. In case of a densitogram consisting of more than five fractions as shown in FIG. 2, however, it was impossible to determine the regular five fractions and calculate integrals, etc. of the individual fractions. Further, in case of a densitogram consisting of four fractions as shown in FIG. 3, it was also impossible to determine the regular five fractions and calculate integrals, etc. of the individual fractions. Therefore, it is required for the inspector to check analog densitograms and electrophoretic patterns, divide a densitogram into five fractions of those of albumin, alpha 1 globulin, alpha 2 globulin, beta globulin and gamma globulin and then perform data processing for recalculation.
In order to determine the regular five fractions of densitograms such as those illustrated in FIG. 2 and FIG. 3 and calculate data such as percentages of integrals of the individual fractions relative to that of the entire densitogram, there has conventionally been used a system described below. A carrier on which samples showing six fractions and four fractions as described above is fed into a densitometer which is separate from a general type of densitometer. The former densitometer is equipped with a photometric system which has the same construction as that shown in FIG. 4 and performs photometry of the samples once again. The densitometer is equipped with a recorder as shown in FIG. 6 which records photometric results on a recording chart paper 21 on a recorder of a densitometer 20 with a recorder pen 22. The densitometer comprises an electric circuit shown in FIG. 7 which consists of an amplifier 25, a logarithmic converter 26, an A/D converter 27, an operation circuit 28 and a D/A converter 29, and records output signals from the D/A converter produced on the basis of the output detected by the photo detector element 7 of the photometric system by operating the recording pen of the recorder shown in FIG. 6. On the other hand, locations corresponding to minimum values (valleys) are determined as boundary points by a boundary point detector 30 arranged in the operation circuit and percentages of integrals of the fractions between the individual pairs of neighboring boundary points relative to that of the entire densitograms are calculated. In FIG. 6, the reference numeral 24 represents boundary buttons which are connected to the boundary point detector 30. Out of these buttons, the "+" pushbutton 24a is so adapted as to set, upon depression thereof, a boundary point for calculation. Speaking more specifically, a section from a position on a densitogram being traced by the recorder pen at the moment of depressing the pushbutton to the next boundary point is determined as a fraction for calculation. It is therefore possible to obtain data on the regular five fractions by depressing the pushbutton at a point which is regarded as corresponding to the fourth boundary point such as b'.sub.4 on a densitogram having four fractions as shown in FIG. 3. Though a densitogram having low slopes is shown in FIG. 3, a densitogram actually consists of fine irregular convexities and concavities. It is therefore possible for an inspector to visually judge the fourth boundary point on a densitogram. The "-" pushbutton 24b is arranged to ignore a valley to be processed as a boundary point when being depressed. In case of a densitogram consisting of six or more fractions as shown in FIG. 2, b.sub.5 is not processed as a boundary point by depressing the pushbutton 24b at the position of b.sub.5 on the densitogram shown in this drawing. That is to say, the pushbutton 24b makes it possible to calculate and record data on the regular five fractions corresponding to A, B, C, D and E shown in FIG. 1.
For determining the fractions with such a conventional system, it is necessary to depress the pushbutton 24a or 24b the moment that the recorder pen just reaches the point b.sub.5 in FIG. 2 or point b'.sub.4 in FIG. 3 while a densitogram is being recorded with the recorder pen 22. The timing to depress the boundary buttons to determine a point to be processed as a boundary point and erase a valley to be ignored as a boundary point must be judged momentarily depending on subjective sense of the operator. Therefore, the pushbuttons are often depressed before and after correct boundary points, thereby causing errors in analytical data in practice.